In the year 2002 Kabushiki Kaisha Toshiba of Kawasaki Japan was issued U.S. Pat. No. 6,396,723 for an invention entitled Rectifier and Transformer Thereof. This invention was developed for use in situations where cooling was either not an issue or if needed in a particular operating environment, a cooling mechanism could be added to ensure that the unit operated safely within its known operating parameters. This product was not originally designed to be utilized by the water and wastewater industry.
A large portion of the assignee of this application's business concerns products for the water and wastewater industry. Applicants were of the opinion that this new full-wave rectifier that converts three phase AC current into DC and also has a transformer that outputs AC current in six phases in a very specific manner, and wherein the current flowing in the DC line through the transformer can be reduced to ½ of the whole in the case of an 18 pulse rectifier, whereby the capacity of the transformer can be reduced as well as its physical size is capable of being reduced, might have applicability in the water and waste water industry if certain issues could be resolved.
The big issue to be resolved, is the ability of the CCD (Toshiba) unit to be operated without the need for added refrigerated air cooling. The primary reasons for wanting to eliminate air conditioning is the major expense of the extra power needed to cool the Toshiba VFD as well as the fact that the use of the VFD would often take place in remote areas where third party air conditioning maintenance might be difficult to obtain, and if obtainable, again might be untimely or extremely costly due to the location of the VFD.
There was a need therefore for the ability to use this new unit of Toshiba in the environments associated with water and wastewater treatment plants in the warm climates of especially California, Arizona, Texas and New Mexico.